1. Field of the Invention
The present invention relates to a distance and light measuring device for a single lens reflex camera.
2. Description of the Prior Art
Most recent single lens reflex cameras have photometers (or light measuring devices) such as TTL exposure meters or TTL automatic controllers for achieving exposure control. A light measuring device of some type is generally essential for any camera.
A variety of TTL automatic control systems are available, and these systems can be divided into two groups. In the first group, the quantity of light from an object to be photographed is controlled through an arithmetic operation after being stored in the system. In the second group, the arithmetic operation is carried out while exposure is performed. A variety of light measuring elements and light measuring optical systems, which are required for controlling the first group, have been proposed, and there is a relatively large degree of freedom in selecting the installation position of the light measuring elements and optical systems. In the second group, it is necessary to measure light which is reflected from the shutter top curtain surface or the film surface. Accordingly, the light measuring element must be positioned in the periphery of the mirror box, and the light measuring element is typically positioned on the bottom of the mirror box.
In addition, the automatic control of a strobe is carried out by a light measuring element which is disposed on the bottom of the mirror box, thus forming a TTL auto strobe.
As is apparent from the above description, in order to achieve exposure control for a single lens reflex camera, installation of the light measuring element on the bottom of the mirror box is considerably important.
On the other hand, not only is the exposure control of the single lens reflex camera automated, the focus detection is also often automated or carried out electrically. Therefore, in such cameras, a focusing indicating device or an automatic focusing device is built into the single lens reflex camera. In the case of a TTL focusing device, its detecting element is, in general, arranged in the camera body. In addition, the best method of setting the detecting element of the focusing device in the camera body without decreasing or lowering the functions and performance of the single lens reflex camera is to arrange it on the bottom of the mirror box.
As the automation, electrical circuitry or system of a single lens reflex camera is improved, the number of sensors is increased. Accordingly, the positions at which these sensors are installed provide other problems.